The present invention relates to a switch and, more particularly, to a push lock switch assembly of push lock switches for use in electrical and electronic equipment for example, for channel selection in television sets, audio appliances, telephones, etc.
Although, there have been proposed, conventionally, various types of push lock switches, the development is mostly focused on their functions, and in such switches the movement of the movable body is strongly resisted by spring means. Therefore, the switches require a comparatively large pushing or manipulating force for depressing the switches to the locked position, so that the operation thereof tends to be somewhat awkward, thus giving a heavy sense of touch to an operator.
Such a push lock switch is well known in the art, and generally includes an elongated housing, and an elongated movable body coaxially housed in said elongated housing. The movable body shifts in the housing between depressed and projected positions, and is normally biased towards the projected position by a spring means. The operation of the switch is such that the depression of the movable body closes the terminals disposed in the housing while projection of the movable body opens the terminals. Therefore, the switch is turned on when the movable body is moved to the depressed position by the application of an external pushing force to the body.
Since the spring means, in such conventional push lock switches, is biasing the movable body in a direction corresponding with the axial direction of the movable body, the external pushing force inevitably increases in relation to the degree of depression of the body in order to operate such switches, thus resulting in a hard touch when switching over such push lock switches. Such being the case, while there is a strong demand in the market for push lock switches which can be comfortably switched over in an easy manner upon mere depression without any disagreeable resistance, there have been none that will fully satisfy such a demand. Moreover, in any attempts to meet such a requirement with conventional constructions of known push lock switches, it is extremely difficult to attain the favorable light touch, and accordingly, development of push lock switches based on an entirely novel conception is necessitated through fundamental improvements of the structures of the known push lock switches.
Another disadvantage inherent in the conventional push lock switches which seek to provide easy operability is that they are liable to be affected by light vibrations or shocks, thus being readily released from their locked state. In order to overcome such drawbacks, some types of the conventional lock switches employ countermeasures to secure them in the locked state through an increase of the force of the spring for urging the movable body, which countermeasures, however, are inconsistent with the smooth operability and agreeable light touch manner during switching over.
Furthermore, in the conventional push lock switches it is difficult to detect whether or not the operating member is fully depressed. In other words, the operating member may be thought to be depressed fully even though it is only depressed halfway, thus presenting possibility of erroneous operation of the switch.